Rock drill



April 0 1926.

L. c. BAYLES ROCK DRILL Filed Oct. 9, 1924 E. i m

Patented Apr. 20, 1926.

j UNITED STATES 1,581,668 PATENT OFFICE. r

LEWIS G. BAYLES, OI EASTON, PENNSYLVANIA, ASSIGNOR TO INGERSOLLBAND'COM-o PANY, 0J3 JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY. I

ROCK DRILL.

Application filed October a, 1924. Serial No. 742,615,

To all whom it may concern:

Be it known that I, Lnwrs O BAYLES, a.

citizen of the United States, and a resident of-i sEaston, county. ofNorthampton, State of Pennsylvania, have invented a certain Rock Drill,ofwhich the following is a specification, accompanied by drawings.

This invention relates to pneumatic drills;

In operating certain types-of pneumatic "drills, such as for instance,those that are a supported by hand, it is desirable that theoperator-pressagainst the tool with considerable force in order that thedrill may opi erate efficiently. Thisis particularly true ofing downhard on such tools with the result that the machine does not produce thedesired result-s. It has been proposed heretofore to construct suchtools so that they stop operating unless theoperator bears down on thetool. This has been accomplished by constructing the cylinder sothat theham mer piston reciprocating therein will overruns the air admlsslonport at thevforward end of the cylinder unless suflicient weight isapplied 'at'the handle end of the tool to keep the steel or anvil blockshoved well up into the pathofthe piston. In this case the hammer pistonstops, being'beyond the ad mission port so as to close it oif. Thisarrangement is not always effectual for the reason that compressionforms on the forward blow of the hammer and causes it to bounce back andreopen theadmission port with the result that the machine continues tooperate. V i

It is anobject of this invention to relieve such compression'and leakageof live air in the front end of the cylinder thereby pre venting thehammer piston from returning when insufiicient pressure is applied tothe handle end of the drill.

Figure l is alongitudinal sectional view of a rock drill adapted tobreak concrete and shows the hammer piston n position cover ing theadmission port at. the front end to prevent operation of the tool, 7

Figure 2 is a longitudinal section of the Other objects and advantageswill be in rock drill shownin Figure 1 in vwhich the drill is shownpushed forward so that the piston cannot advance to cover the admis sionport, and a r i I Figure 3 is a cross sectional view taken along theline v 'lhedrawing illustrates a drill in theform of a concretebreakerwhich is provided with" a sharp pointed steel A for splitting oficon crete in chunks and is a substitute for the old fashioned method ofusing a hand ham-Q;

mer and, chisel. The, drill for operating against thesteel A may be ofanyisuitable type,that shownin the drawing being of the well knownsemi-valvelesstyPe. I

The drill comprises a cylinder B within which there isprovidedareciprocating pis ton iG adapted to strike against an anvil block 1)supported in the anvil block seat E 1 and in contact with the drillsteelfA sup.-

ported by a front head F. The anvil block 1) is arranged to moveforwardly or back in the seat E so as to provide a certain freedom ofmovement desirable to permit the steel A to move forwardly and backvwith respect to thecylinderB. p i

As these tools have usually been con structed, it is necessary to presswith con siderable force on a handle G provided at the, rear'end ofthedrill in order to keep the anvil block" D push-edowell up 'into thecylinder B, for if the anvil block D- is perk" mitted to slide forwardlywhile the piston O is reciprocating, the latter will either strikeagainst" the anvil block seat E or will strike the anvil block when isin contact with the front head F as shown in Figure 1 and the force-ofthe hannnerblows is taken signed to withstand shocks of this sort andafter a short time the drill is; ruined. It has heretofore been proposedto avoid this difficulty by locating the admission port H so that thepiston O overruns it andcuts olf the/supply of motive fluidto the frontend of the oylinder'B when the anvil block D 7 is permitted to advancein the seat E beyond a certain limit. The piston C is then sup posed tostop operating although the throttle valve J may still be opened becausesubstantially no motive fluid is admitted inthe cylinder B vahead oftheback. a

One dilficulty with this arrangement as" piston C todrive it 7 C for thereason that the space behindthe heretofore proposed is that when thepiston is exposed to atmospheric pressure on its rearward face and tocompression on its for- T )lock 1) piston isin communication withatmosphere while the space ahead of the piston is not; Practically fulllive air pressure slowly builds up at the front of the piston C whicheventually drives the piston back to uncover the port H and therefore torecommence its reciprocation. If the drill is com paratively new thesame result obtains for the reasonthat thecompression pressure, isrelatively high ahead of the pistonrbecanse ofthe tight fit between itandthe cylinder B; The piston C bounces back and reopens the admissionport H. This condition is probably worse than when the drill is old andthe cylinder walls and piston become somewhat worn because" thereciprocation due to high compression is much more rapid.

By this invention the return of the pis' ton C after passing tlieport Hand closing it as is prevented by means to-"eliminate compression atthis point, including longitudinal grooves K in the cylinder walls,extending from the forward end ofithecyliin der B beyond the inlet portHywhich are arranged to connect th spaces on opposite sides 'ofthepiston only when the piston is permitted to advance to "cover the inlet'port The grooves K extend fronithe extreme endjof the cylinder B toa'point'ilocated at r the rear end of the head of the piston G when thefront edge of the piston is just covering the port H. Therefore, whenthe;

drill is operating normally, the" grooves Kf are inoperative, they donot relieve the compression at thefrontend' of the cylinder nor do tl1ey,in'a1'1y way effect the operation of the tool. However whenithepressur'e I on the handle G is insuflicient to hold the drillproperly down against the steel the anvil block D advances permittingthe piston C tolengthen its stroke beyond the port H, and therefore, toceasepperating, the compression ahead of the piston being relieved byleaking out through the grooves K to atmosphere through the main airexhaustL. Nor can the piston C be caused to start again by air leakingdown past the piston from the port because such leakage'air also findsits way to atmosphere by' way of the gro'oves During normal, operationthe piston 0 advances no farther than approximately half way coveringthe port H as shown in Figure 2fland the anvil block D is seated in theanvil block. seat E. However, as the pres- :ure is relieved on thehandle G the anvil is pushed forwardly with respect to the seat- E andthe return of the piston C on the back stroke is ,feebler since theadmission of live air-through the port H is somewhat cut off.

Although the main objectof stopping the 7 operation of the piston C asabove described is to prevent the piston from breaking the front partsof the drill, in addition the arrangement insures that the operator willpress sufliciently hard against the handle G of the'tool to keep thesteel Apressed hard against the work, and thereforejto prevent carelessoperation on the part of the operator. -Poor operators are apt to allowtheir tools to keep on operatingwith the least possible exertion ontheir part with the result that very little workis doneby'the tool.

\Vith the above described arrange 'ment' as soon as the operator relaxesthe tool stops operating automatically.

Any suitable piston and valve action may be employed for the drill.

That shown in the drawing is ofthesemi-valvelesstype in'-- which thepiston C is provided with the rearward-extension 0 working in a smallbore P of the cylind-er'B and subjected to constant pressure admittedthrough the pas sage Q in the back head R. The control of the air foroperating the piston is'w'ell' known, having been describedgin patent toL12. Bayles, No.1,096,987, issued May-19,

The throttle valve J is controlled by means of a lever S arranged topress against the stem of the valve J and adapted to be manuallycontrolled by a lever T working in'a slot U in thehandle G. The steelAis held within the'front head F by means of a suitable steel retainer Vcooperating with I the usual form ofcollar shank of the steel. 1

I claim:

normally adapted to extend a substantial distance into said cylinder, ahammer piston in thecylinder for delivering blows-to the upset I on thei L 1. A rock drill comprising a cylinder havv ing inlet and exhaustports, an anvil block der being provided with grooves to bypass leakageair from the front end of the cylinder to atmosphere when the inlet portis closed by the piston in order to prevent the piston from reboundinguponthe' completion of its forward stroke due to an air cushion built upin the forward end of the cylinder. 7

2. A rock drillcomprising a cylinder hav-:

ing inlet and exhaust ports, an anvil block normally adapted to "extendsubstantial distance into said cylmder, a hammer lpiston in the cylinderfor delivering blows to forwardly and the port is covered by the theanvil block and adapted to close the inpiston in order to prevent thepiston from 1 let port when the anvil is moved forwardly rebounding uponthe completion of its forfrom its normal position, said cylinder hav-Ward stroke due to an air cushion built up ing longitudinal grooves onopposite sides of in the forward end of the cylinder.

the inlet port to permit the escape of leakt In testimony whereof I havesigned this age air from the front end of the cylinder specification.

to atmosphere When the anvil block is moved LEWIS C. BAYLES.

